Forecast of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2010 – by Colorado State University

FORECAST OF ATLANTIC SEASONAL HURRICANE ACTIVITY AND LANDFALL STRIKE PROBABILITY FOR 2012 (as of August 3, 2012) by Philip J. Klotzbach and William M. Gray

We anticipate a slightly-below average remainder of the hurricane season this year due to an anticipated weak El Niño event and a tropical Atlantic that is less favorable than in the past two years. This forecast is a slight increase from activity predicted in early June, due to a slower-than-anticipated onset of El Niño and a somewhat more favorable tropical Atlantic than observed earlier this year. We expect a slightly below-average probability of United States and Caribbean major hurricane landfall.ATLANTIC BASIN SEASONAL HURRICANE FORECAST FOR 2012

POST-31 JULY PROBABILITIES FOR AT LEAST ONE MAJOR (CATEGORY 3-4-5) HURRICANE LANDFALL ON EACH OF THE FOLLOWING UNITED STATES COASTAL AREAS:

1)Entire U.S. coastline – 48% (full-season average for last century is 52%)2)U.S. East Coast Including Peninsula Florida – 28% (full-season average for last century is 31%)3)Gulf Coast from the Florida Panhandle westward to Brownsville – 28% (full-season average for last century is 30%)

POST-31 JULY PROBABILITIES FOR AT LEAST ONE MAJOR (CATEGORY 3-4-5) HURRICANE TRACKING INTO THE CARIBBEAN (10-20°N, 60-88°W)

1) 39% (full-season average for last century is 42%)

POST-31 JULY HURRICANE IMPACT PROBABILITIES FOR 2012 (NUMBERS IN PARENTHESES ARE LONG-PERIOD FULL SEASON AVERAGES)

State Hurricane Major HurricaneFlorida 47% (51%) 19% (21%)

transit.org/hurricane for landfall probabilities for 11 U.S. coastal regions and 205 coastal and near-coastal counties from Brownsville, Texas to Eastport, Maine as well as probabilities for every island in the Caribbean. We suggest that all coastal residents visit the Landfall Probability Webpage for their individual location probabilities.

ABSTRACTInformation obtained through July 2012 indicates that the remainder of the 2012 Atlantic hurricane season will be slightly less active than the average 1981-2010 season. We estimate that the remainder of 2012 will have about 5 hurricanes (average is 5.5), 10 named storms (average is 10.5), 37.25 named storm days (average is 58), 19.25 hurricane days (average is 21.3), 2 major (Category 3-4-5) hurricanes (average is 2.0) and 5 major hurricane days (average is 3.9). The probability of U.S. major hurricane landfall and Caribbean major hurricane activity for the remainder of the 2012 season is estimated to be slightly below its long-period average. We expect the remainder of the Atlantic basin hurricane season to accrue Net Tropical Cyclone (NTC) activity of approximately 90 percent of the seasonal average. We have increased our seasonal forecast from early April and early June, due to a combination of uncertainty in El Niño as well as slightly more favorable tropical Atlantic conditions.This forecast was based on a newly-developed extended-range early August statistical prediction scheme developed over the previous 33 years. Our two older statistical forecast models that have been utilized for the past few years were consulted. Analog predictors were also considered.The ENSO-related warming trend in the tropical Pacific has slackened somewhat in recent weeks, and we are unsure as to how much of an impact El Niño will have on this year’s hurricane season. The combination of the uncertainty in tropical Pacific conditions along with the low sea level pressure anomalies observed in recent weeks over the tropical Atlantic have led us to increase our forecast slightly.

Starting today and issued every two weeks following (e.g., August 17, August 31, etc), we will issue two-week forecasts for Atlantic TC activity during the peak of the Atlantic hurricane season from August-October. A late-season forecast for the Caribbean basin will be issued on Monday, October 1.